This invention concerns a self-locking belt roller, especially for motor vehicle safety belts, having a vehicle-sensitive and/or belt-sensitive control system for a locking element, which in the blocking condition prevents further rotation of the belt winding shaft, and having a winding-up spring acting on the belt winding shaft.
A belt roller of this type is described for example in DE-GM 74 25 341. The belt roller has an associated vehicle-sensitive and a belt-sensitive control system, which, when accelerations or decelerations act on the vehicle or when belt extraction occurs too fast, moves the locking element, mounted on the belt winding shaft so that it can be pivoted out radially, into a housing-fixed teeth arrangement and thus effects locking of further unwinding movement of the belt winding shaft. Through a loosening of the belt over a small retracting path into the belt roller, the blocking of the locking element is cancelled and the self-locking belt roller is again ready for use.
For certain cases of application it is required that, with such a self-locking belt roller, equipped with a vehicle-sensitive and/or a belt-sensitive control system, in certain operational positions the blocking system should be connected permanently so that after reaching a certain operational position of belt extraction only a winding-up of the belt is still possible without the possibility of a renewed belt extraction, whereby the blocking readiness of the self-locking belt roller is only reinstated when the belt is sufficiently retracted. Such a case of application exists especially when a child's seat is to be fastened in t he vehicle with the self-locking belt roller. In this connection, a length of belt is extracted from the self-locking belt roller and guided around and engaged with suitably configured attachment points on the child's seat. Since the self-locking belt roller only locks in cases of emergency, the child's seat cannot be fastened down in the vehicle because the bracing of the belt is only determined by the force of the winding-up spring. In addition, the child sitting in the child's seat can extract more belt from the self-locking belt roller in a playful manner so that when an accident occurs belt slack is present and the child's seat is no longer fastened securely in the vehicle. On the other hand, however, there is the requirement that the normal functional behavior of a self-locking belt roller should be present when an older child or adult is to be secured by it, in order to utilize the comfort offered by a self-locking belt roller.
In the prior art, corresponding for example to DE-OS 36 15 443, so-called semiautomatic machines are known, in which during the extraction movement of the belt from the belt winding shaft the blocking system is disconnected and is only connected by the belt returning a little way onto the belt roller. With such belt rollers the connection of the blocking system takes place permanently, that is to say when the blocking system is connected the belt winding shaft is constantly blocked. In this way, indeed, a child's seat can be secured adequately although when an older child or adult uses the safety-belt system the advantages of a self-locking belt roller are lost, such as the freedom of movement of the person buckled-in due to the fact that the belt can be extracted from the belt roller and the belt roller is only brought into the blocking position, when an accident occurs, by means of the vehicle-sensitive or belt-sensitive control system.
The object of the invention therefore is to create a self-locking belt roller of the type named at the beginning, in which in a predetermined operational state a winding-up of the belt is possible, although an extraction of the belt is prevented.
This object including advantageous developments and further embodiments is achieved by the present invention as disclosed by the following description and claims.